Traditional electromechanical cables are comprised of a core containing one or more insulated electric conductors and covered by two layers of helical pattern oppositely wound steel armor wires. Typically, the inner layer of wires in contact with the insulation material is wrapped in a right-hand lay. The outer layer of wires, to overcome the tendency of the cable itself to rotate, is wrapped over the inner layer in a left-hand lay pattern. These cables are used in the oil exploration industry for detonating explosives to "open" a field and in well logging operations. Over time, because of wear, corrosion, bending, fatigue, torque, rotation, physical damage, etc., these cables present loose armor, gaps in armor, broken armor wires, electrical leakage or break down, etc., and are required to be repaired. Therefore, electromechanical cables are frequently spliced.
For example, traditional methods of splicing a double-armored cable presenting an electrical break down include approximately six steps. The first step is to locate the short circuit spot in the cable using a traditional process of determining the resistance at whip end, at drum end and of the line with a battery and a digital voltmeter, then applying a formula to determine the distance from one cable end to the shortcut. The second step is to cut the cable at the short circuit spot. The third step is to reestablish the conductivity at the spot. The fourth step is to reestablish the insulation over the electrical conductor(s). The fifth step is to resplice the inner metallic armor. The sixth step is to splice and fasten the outer armor wires together.
The first five steps are commonly done to most repair methods. The splicing of the outer armor layer referenced in the sixth step has usually been accomplished by two different techniques, one referred to as silver brazing and the other one as "shiming" with metal foils (brazed splice or "shimed" splice).
The silver-braze technique uses an oxi-acetelene torch or equivalent machine to weld the adjacent outer wires to one another in order to avoid their unwinding. Although the silver brazing technique assures the tips of the cut wires will stay in place, it has several problems caused by the welding spots. These spots affect the mechanical conditions of the cable since the brazed wires at their welding points are rigid, thus not movable. These rigid and non-bendable spots increase the friction of the cable within logging holes, which accelerates the wear and tear of the cable itself. Furthermore, the welding spots produce lumps that increase the diameter of the cable making it impossible to reuse it in cased hole operations since the lumps can cause the cable to get stuck in the pipe.
The technique of "shiming" with metal holding foils uses stainless steel foils to hold together the adjacent cut wire ends in order to stop their unwinding. Typically the cut wire ends are pressed together between a stainless steel foil and the inner metallic wound armor of the cable, and then the foil ends are inserted between the inner and outer armor wires of the cable. Although the shiming technique allows the spliced wires to retain their individual flexibility, this technique also has serious drawbacks. For example, cables having the foil repair cannot be used in cased hole operations since typical high-pressure flow from the well would displace the foils exposing and allowing the tip ends of the cut wire to separate.
Many U.S. patents have been proposed to resplice together cut cables. See for example U.S. Pat. Nos. 3,259,969 and 3,828,601 and 3,934,784 to Tessman; U.S. Pat. No. 3,956,877 to Gilmore; U.S. Pat. No. 4,079,189 to Troccoli; U.S. Pat. Nos. 4,317,003 and 4,367,917 and 4,407,065 to Gray; U.S. Pat. No. 4,408,828 to Le Noane et al. U.S. Pat. No. 4,496,795 to Konnik; U.S. Pat. No. 4,585,304 to Winter et al. However, none of the patents overcome all the problems mentioned above.